The present invention relates to an emergency lighting arrangement configured to be connected to a supply network, comprising: an electronic ballast for igniting and burning a fluorescent lamp, and to an emergency lighting apparatus, comprising: a battery, a recharging device for recharging the battery from the supply network, a supply device for supplying the battery voltage further, and a control unit configured to control the devices of the emergency lighting apparatus.
Emergency lighting is installed in public buildings and other public premises to secure at least minimum lighting in the case of a disturbance or a power failure in the supply network. The aim of emergency lighting is to illuminate specific premises according to regulations to allow safe exit from the premises, for example, when the supply network malfunctions due to network failure, for example. Emergency lighting can be implemented using lighting devices designed for normal general lighting and provided with an emergency lighting apparatus. Emergency lighting apparatuses are placed in connection with those lighting devices that are to produce the emergency lighting.
Currently known, separately placed emergency lighting apparatuses comprise a recharging device, a battery, an electronic ballast, and a power supply exchanger for a fluorescent lamp. The principle of operation is that under normal circumstances, i.e. when mains voltage is on, the emergency lighting apparatus recharges the battery, and the fluorescent lamp is operated either by a magnetic choke or an electronic ballast. A power failure causes an internal ballast provided in the emergency lighting apparatus to switch on, and the power supply exchanger coupled to the lighting apparatus wiring connects the fluorescent lamp to the ballast of the emergency lighting apparatus. Due to limited battery capacity, the internal ballast of the emergency lighting apparatus must be dimensioned so that during a power failure it supplies the fluorescent lamp with power producing a lighting intensity that is considerably lower than normal to allow a sufficiently long operating time to be achieved.
A problem with this technology is that the coupling of the power supply exchanger to the lighting apparatus wiring, i.e. the four wires of a fluorescent lamp, renders the wiring complicated as regards installation. Moreover, this sets additional requirements for the power supply exchanger, because it must be capable of sustaining the ignition voltage of the fluorescent lamp, the maximum value of which may be over 1 kW. Further, during a power failure a fluorescent lamp is usually employed without filament voltage, which decreases the service life of the fluorescent lamp.
Current technology enables normal fluorescent lamp to be dimmed by means of specific dimming ballasts. Such ballasts are commercially available, and they allow the current flowing from the ballast to the fluorescent lamp, and thereby the illumination produced by the fluorescent lamp, to be adjusted. When used in connection with general lighting, a dimming ballast is normally used for dimming the lighting.
WO0027013 discloses an emergency lighting apparatus that can be coupled between alternating voltage and the ballast of a fluorescent lamp. When a network failure occurs, the emergency lighting apparatus supplies direct voltage of a predetermined magnitude to the ballast to allow the fluorescent lamp to burn.
It is an object of the present invention to provide an emergency lighting arrangement, which avoids the above disadvantages and provides a simple arrangement enabling reliable use of emergency lighting in a manner that allows the service life of the battery capacity of the emergency lighting apparatus to be optimised. This object is achieved by an arrangement of the invention, characterized in that the electronic ballast is a controllably dimmable ballast and that the emergency lighting apparatus further contains means for controlling the dimming of the electronic ballast, which means comprise a battery current determining member, whereby the means for controlling the dimming of the electronic ballast are configured to control the dimming of the electronic ballast in response to the magnitude of the determined current.
The arrangement of the invention is based on the idea that the emergency lighting arrangement is provided with a dimmable electronic ballast and the emergency lighting apparatus is equipped with means for dimming the dimmable ballast. Due to the dimming, the input power of the ballast decreases during a power failure, whereby the emergency lighting apparatus that supplies power to the ballast can be provided with lower battery capacity than before.
The dimming adjustment allows the input power of the ballast to be controlled to an optimal level in relation to battery capacity for the required operating period during power failure. In addition, this characteristic allows one and the same emergency lighting apparatus to be used in connection with lamps of different power levels.
An emergency lighting arrangement based on the same principle of the invention is also applicable in connection with dimmable ballasts of different types.
The invention further relates to an emergency lighting apparatus which is configured to be coupled between a dimmable electronic ballast and a supply network, the emergency lighting apparatus comprising a battery, a recharging device for recharging the battery from the supply network, a supply device for supplying the battery voltage further, and a control unit which is configured to control the devices of the emergency lighting apparatus. The emergency lighting apparatus is characterised in that it further comprises means for controlling the dimming of the electronic ballast.
The emergency lighting apparatus of the invention provides a simple and reliable structure for implementing the advantages of the emergency lighting arrangement. The emergency lighting apparatus of the invention can be connected to commercially available dimmable electronic ballasts.